CN108368564B - Method for fixing arsenic and arsenic-containing glass solidified body - Google Patents

Abstract

The present invention provides a method for fixing arsenic, which is characterized in that arsenic is made into a glass solidified body by adding calcium arsenate to a vitrified material containing iron, silica and an alkaline component so that the weight ratio of iron to silica is 0.5 to 0.9 and the alkaline component amount is 14 to 26 wt%.

Description

Arsenic fixation method and arsenic-containing glass solidified body

technical field

The present invention relates to an arsenic fixation method and an arsenic-containing glass solidified body to produce a glass solidified body in which the amount of arsenic elution is limited to an environmental standard or less. More specifically, it relates to an arsenic fixation method capable of limiting the amount of arsenic eluted to an environmental standard or less by making calcium arsenate recovered from a smelting intermediate or the like into a glass solidified body, and an arsenic-containing glass obtained by the method. solidified body. The arsenic fixation method of the present invention is suitable as a treatment method for arsenic-containing copper slime or the like produced in a copper smelting process.

This application claims priority based on Japanese Patent Application No. 2015-250760 filed in Japan on December 23, 2015, the content of which is incorporated herein by reference.

Background technique

In the electrolytic smelting of copper, copper and arsenic gradually accumulate in the electrolyte. Therefore, a part of the electrolyte is extracted for liquid purification treatment. When this liquid purification treatment is performed, sludge containing copper arsenide (Cu ₃ As, etc.) is extracted. The arsenide-containing copper slime contains approximately 40 to 60 mass % of copper, 20 to 40 mass % of arsenic, and 0.5 to 5 mass % of lead, tin, antimony, bismuth, and the like, respectively. Therefore, after removing impurities such as arsenic, the arsenide-containing copper slime is returned to the copper smelting process, and the copper component is recovered from the arsenide-containing copper slime. On the other hand, since impurities such as arsenic gradually accumulate in the copper smelting system and have a bad influence on the quality of copper, the impurities such as arsenic are excluded from the system.

As a method of fixing arsenic contained in arsenide-containing copper slime and the like to a stable compound and removing the arsenic out of the copper smelting system, for example, the following processing methods have been conventionally known.

In the method disclosed in Patent Document 1, first, a sodium hydroxide solution is added to a copper-arsenic-containing material, and air is blown in to perform alkaline oxidative leaching in a heated state. Next, after the leaching is completed, the pH of the liquid to be treated is adjusted to pH 7.5 to 10, and solid-liquid separation is performed into a leaching residue containing copper components and a solution containing arsenic. Next, a trivalent iron compound is added to the arsenic-containing solution so that the Fe/As molar ratio becomes 0.9 to 1.1 to generate FeAs precipitates, and the FeAs precipitates recovered by solid-liquid separation are mixed with a sulfuric acid solution , so as to make acid slurry or acid solution. Next, the slurry or the solution is heat-treated to produce crystalline scorodite (FeAsO ₄ ·2H ₂ O), thereby immobilizing arsenic.

In the method disclosed in Patent Document 2, first, arsenous acid (As ₂ O ₃ ) is extracted by leaching water from arsenic-containing soot in a heated state. Next, an oxidizing agent (manganese peroxide or the like) and slaked lime are added and reacted to the filtrate, and calcium arsenate is produced and recovered. Next, the recycled glass frit was mixed with this calcium arsenate and melted at 1200° C. to produce an arsenic-containing glass solidified body.

In the method disclosed in Patent Document 3, first, sodium-based alkali slag containing arsenic and antimony is heated to 850 to 1200° C. to selectively reduce and separate antimony generated from a carbon-based reducing agent. Next, a glass component is added to the remaining sodium arsenate, and it is heated and melted to produce a glass solidified body of arsenic.

In the method disclosed in Non-Patent Document 1, under a constant oxygen partial pressure, CaO—SiO ₂ based slag and calcium arsenate are heated and melted at 1400° C. to produce an arsenic glass solidified body.

Patent Document 1: Japanese Patent Laid-Open No. 2014-208581

Patent Document 2: International Publication WO2014/059535A1

Patent Document 3: Chinese Patent Publication CN102965517A

Non-patent document 1: Paper presented at GDMB Seminar "Slags in Metallurgy (Schlacken in der Metallurgie)" P.M.SWASH et al.Aachen, Germany, 17-19March, 1999.

The treatment method of Patent Document 1 has the advantages that arsenic is fixed as scorodite, the arsenic concentration in scorodite is high, and the conversion efficiency from the iron-arsenic precipitate as an intermediate product to scorodite is also good. On the other hand, when an iron-arsenic precipitate is formed, an expensive divalent iron salt is used, which tends to increase the cost. In addition, after the scorodite is synthesized, the adhering arsenic is removed by washing with water, so that an arsenic-containing waste liquid is generated, and the treatment cost is increased. Moreover, since the volume specific gravity of scorodite is about 1, which is small, if the scorodite is disposed of in the state, the volume of the processing site is compressed.

In the treatment method of Patent Document 2, the process of leaching arsenic-containing soot with water, filtering an arsenous acid solution, and adding magnesium oxide and slaked lime to the solution to prepare calcium arsenate is labor-intensive and expensive. In addition, there is a problem that the fixation of arsenic contained in the glass solidified body is insufficient.

The treatment method of Patent Document 3 is a method of vitrifying sodium arsenate, and since this method volatilizes arsenic oxide at a temperature of 1000° C. or higher, exhaust gas treatment is difficult.

In the treatment method of Non-Patent Document 1, in order to vitrify calcium arsenate under a constant oxygen partial pressure using CaO—SiO ₂ slag, it is necessary to appropriately control the oxygen partial pressure, and there is a problem that the actual operation is difficult.

SUMMARY OF THE INVENTION

Regarding the processing method for vitrifying and fixing arsenic, the present invention provides a glass fixing method of arsenic that solves the above-mentioned problems in the conventional processing methods, and an arsenic-containing glass solidified body obtained by the method. According to the present invention, efficient and easy glass immobilization of arsenic can be achieved, and the elution amount of arsenic contained in the glass solidified body can be made to be equal to or less than the environmental standard.

The aspect of the present invention relates to an arsenic fixation method and an arsenic-containing glass solidified body having the following structures (hereinafter, referred to as "arsenic fixation method of the present invention" and "arsenic-containing glass solidified body of the present invention"). .

[1] A method for immobilizing arsenic, comprising iron and silica in a manner such that the weight ratio of iron to silica is 0.5 to 0.9 and the amount of basic components is 14 to 26 wt % Calcium arsenate is added to the vitrification material of the basic component, and the arsenic is made into a glass solidified body.

[2] The method for fixing arsenic according to the above [1], wherein an alkaline solution and an oxidizing agent are added to the copper-arsenic-containing substance to perform oxidative leaching, the leaching residue is subjected to solid-liquid separation, and the recovered arsenic acid is alkaline Slaked lime is added to the solution to generate calcium arsenate, and the vitrified material is added to the recovered calcium arsenate so that the weight ratio of iron to silica and the amount of the basic component are as described above. Made of glass solidified body.

[3] The method for fixing arsenic according to the above [2], wherein the copper-arsenic-containing material is arsenide-containing copper slime, and sodium hydroxide and an oxidizing agent are added to the arsenic-containing copper slime and heated to make the arsenic In leaching, on the other hand, the leaching residue is subjected to solid-liquid separation, and slaked lime is added to the recovered sodium arsenate solution to generate calcium arsenate, and the above-mentioned weight ratio of iron to silica and the above-mentioned amount of alkaline components are obtained. By adding the above-mentioned vitrifying material to the recovered calcium arsenate, calcium arsenate is made into a glass solidified body.

[4] The method for fixing arsenic according to the above [3], wherein slaked lime is added to a sodium arsenate solution to generate calcium arsenate, and the solution containing the calcium arsenate is subjected to solid-liquid separation to recover calcium arsenate On the other hand, the filtrate containing sodium hydroxide is returned to the oxidative leaching process and reused as an alkali source for oxidative leaching.

[5] An arsenic-containing glass solidified body, characterized in that the arsenic content is 5% by weight to 15% by weight, the weight ratio of iron to silica is 0.5 to 0.9, and the total amount of basic components Na ₂ O and CaO It is 14 weight% - 26 weight%.

The glass solidified body produced by the arsenic fixing method of the present invention can be stored as a model for a long period of time, and therefore can be stored stably without scattering like scorodite which is a powder.

According to the arsenic fixing method of the present invention, the arsenic concentration in the glass solidified body can be increased to 13% by weight or more in the glass solidified body using waste glass, and the glass solidified body can be increased in the glass solidified body using copper slag. The arsenic concentration was increased to more than 11% by weight. Since the volume of each of these glass solidified bodies is smaller than that of scorodite, the limited volume of the final treatment site can be effectively utilized.

In the arsenic fixation method of the present invention, sodium arsenate is recovered by oxidative leaching using sodium hydroxide, and calcium arsenate produced by adding slaked lime to the sodium arsenate solution can be used. In this case, since sodium hydroxide is produced together with the production of calcium arsenate, most of the sodium hydroxide can be returned to the leaching step and reused. Therefore, sodium hydroxide can be effectively used, and its consumption can be reduced.

The arsenic fixation method of the present invention is a method of vitrifying and fixing calcium arsenate, and is not an iron-arsenic precipitate formed by adding a ferric compound to an arsenic acid alkaline solution as in the conventional method. Therefore, it is possible to reduce the processing cost without using an expensive ferric compound.

Unlike scorodite, the arsenic-containing vitrified body produced by the arsenic fixation method of the present invention does not need to be washed with water, and the arsenic content of the waste liquid is small, so the burden of waste liquid treatment is small.

In addition, in many cases, waste glass contains a trace amount of arsenic, so it is difficult to recycle and recycle, and most of them are disposed of in landfills. However, according to the method for fixing arsenic of the present invention, the arsenic concentration of the glass solidified body can be increased, so it is different from the arsenic concentration of the glass solidified body. Compared with the landfill treatment in the state of waste glass, the limited volume of the final treatment site can be effectively utilized.

Description of drawings

FIG. 1 is a process diagram showing the processing steps of the present invention.

Detailed ways

Hereinafter, embodiments of the arsenic fixation method and the arsenic-containing glass solidified body of the present invention will be described.

The method for immobilizing arsenic according to the present invention is characterized by comprising iron, silica, and an alkali such that the weight ratio of iron to silica is 0.5 to 0.9 and the amount of basic components is 14 to 26 wt %. Calcium arsenate is added to the vitrification material of the natural component to make arsenic into a glass solidified body.

As the above calcium arsenate, for example, calcium arsenate produced by adding slaked lime to an arsenic-acid alkaline solution obtained by adding an alkaline solution and an oxidizing agent to copper-arsenic-containing substances to perform oxidative leaching can be used. recycled. As the copper-arsenic-containing material, for example, arsenic-containing copper slime or the like produced in copper electrolytic smelting can be used. As the above-mentioned alkaline solution, a sodium hydroxide solution can be used.

The arsenic-containing copper slime produced in copper electrolytic smelting is recovered, washed with water, added with sodium hydroxide to make pH 7.5 or higher, and heated by adding an oxidant to leaching out arsenic, and the leaching solution is subjected to solid-liquid separation to recover arsenic sodium arsenate solution, and calcium arsenate is produced when slaked lime is added to the sodium arsenate solution. As calcium arsenate used in the arsenic fixation method of the present invention, calcium arsenate recovered from an arsenide-containing copper slime solution produced in such copper electrolytic refining can be used. Hereinafter, the step of recovering calcium arsenate from the copper arsenide-containing sludge solution and vitrifying will be described. In addition, the process is shown in FIG. 1 .

[Alkaline oxidation leaching process]

Arsenic is leached by adding an alkaline solution and an oxidizing agent to the copper arsenide-containing mud. In the alkaline oxidative leaching, the pH of the solution is preferably 7.5 or more. As the oxidizing agent, air and oxygen, chlorine, chlorine compounds, and the like can be used. Air and oxygen can be blown into the solution in the form of microbubbles. The heating temperature for oxidative leaching is preferably 90°C or lower.

In the oxidative leaching using a sodium hydroxide solution as an alkaline solution, as shown in the following formula [1], copper arsenide is oxidized in the sodium hydroxide solution, and copper turns into copper oxide or copper hydroxide and becomes a solid residue , arsenic forms sodium arsenate and leaches out in solution.

2Cu ₃ As+4NaOH+4O ₂ =3Cu ₂ O↓+2Na ₂ HAsO ₄ +H ₂ O [1]

In the region where the pH of the above alkaline oxidation leaching is lower than 7.5, for example, a trace amount of copper ions and arsenic (V) ions react to form copper arsenate [Cu ₃ (AsO ₄ ) ₂ ] precipitation, so the arsenic concentration in the solution reduce. When sodium hydroxide is added and the pH is adjusted to 7.5 or more, leaching of arsenic is performed, so it is preferable to adjust the pH to 7.5 or more and perform oxidative leaching.

As shown in the above-mentioned reaction formula [1], 2 mol of sodium hydroxide is consumed for oxidative leaching of 1 mol of arsenic. Therefore, the amount of NaOH added can be adjusted according to the NaOH/As molar ratio=2 times (1 equivalent). In addition, when the arsenic concentration in the raw material is clear, a desired amount of the total amount of sodium hydroxide may be added at the start of leaching. In this case, even if the liquid properties at the initial stage of leaching become strongly alkaline (about pH 14), if the pH at the end of leaching is set to be in the range of 7.5 to 10, the concentration of heavy metal ions such as copper and lead is limited, so that it is possible to obtain Arsenic leachate containing higher purity arsenic (V).

The leaching temperature is preferably 30°C to 90°C. If the temperature is lower than 30°C, the leaching time becomes longer. If the temperature is higher than 90°C, the amount of steam generated increases, resulting in waste of heating costs.

According to the above alkaline oxidative leaching, arsenic is selectively leached from the arsenide-containing copper slime, and the separation from coexisting metals such as copper and lead contained in the slime is good. Furthermore, the filterability of the slurry after leaching is good, and filtration can be performed in a short time. In addition, the mass of copper contained in the leaching residue is as high as 80 to 85%, and copper smelting treatment is easy.

[Production process of calcium arsenate]

The leaching solution obtained by the above alkaline oxidation leaching is subjected to solid-liquid separation to remove the leaching residue containing copper oxide, and the sodium arsenate solution of the filtrate is recovered. When slaked lime is added to this sodium arsenate solution, calcium arsenate (As ₃ Ca ₅ O ₁₃ H) is produced as shown in the following formula [2]. The calcium arsenate is recovered.

3Na ₂ HAsO ₄ +5Ca(OH) ₂ =6NaOH+As ₃ Ca ₅ O ₁₃ H↓+3H ₂ O [2]

In the production step of calcium arsenate, as shown in the above reaction formula [2], the amount of slaked lime produced by calcium arsenate is 5/3 in the molar ratio of Ca/As, so the molar ratio of added Ca/As is 1.7 Slaked lime in an amount of ~2.0 is sufficient. When the molar ratio of Ca/As is 1.7 or less, the recovery rate of As decreases, and when it is 2.0 or more, unreacted slaked lime remains as an impurity, which is not preferable.

In addition, as shown in the above-mentioned reaction formula [2], calcium arsenate and sodium hydroxide are produced together, so the sodium hydroxide contained in the filtrate in which the solid-liquid separation of calcium arsenate has been carried out is returned to the above-mentioned oxidative leaching step, It can be reused as an alkali source.

In the production step of calcium arsenate, the pH of the solution is preferably 7.5 to 11, and the pH is more preferably 9 to 10. When the pH is less than 7.5, the concentration of sodium hydroxide to be regenerated decreases as shown in the following formula [3], and when the pH is 11 or more, the production of calcium arsenate is insufficient, which is not preferable.

3NaH ₂ AsO ₄ +5Ca(OH) ₂ =3NaOH+As ₃ Ca ₅ O ₁₃ H↓+6H ₂ O [3]

The solution temperature in the calcium arsenate production step is preferably 50°C to 70°C. If the solution temperature is lower than 50°C, calcium arsenate will not be sufficiently produced. When the solution temperature exceeds 70° C., crystalline calcium arsenate grows around calcium hydroxide, which inhibits the reaction, which is not preferable. The heating time is preferably 1 to 4 hours.

[Vitrification process of calcium arsenate]

adding a vitrifying material containing iron, silica and basic components to calcium arsenate so that the weight ratio of iron to silica is 0.5 to 0.9 and the amount of basic components is 14 to 26 wt %, Thereby, calcium arsenate is made into a glass solidified body.

The weight ratio of iron to silica is the ratio of the weight of iron contained in the vitrified material to the weight of silica contained in the vitrified material.

The weight percentage of the amount of the basic component is the percentage of the weight of the basic component to the total weight of the dry weight of calcium arsenate and the weight of the vitrified material.

The weight in this specification is used with the same meaning as mass. Thus, the weight ratio is the mass ratio, and the weight % is the mass %.

As the vitrification material containing iron, silica, and an alkaline component, for example, waste glass containing iron, silica, calcium, and sodium, copper slag, and the like can be used. The waste glass and the copper slag may be mixed with silica sand or the like as a silica source so that the weight ratio of iron and silica and the amount of the basic component of the present invention fall within the ranges. In addition, waste glass and copper slag may be mixed and used.

The vitrified material and calcium arsenate are mixed and heated so that the weight ratio (Fe/SiO2) of iron and silica in the vitrified body is 0.5 to 0.9 and the amount of the basic component is 14 to 26% by weight It is melted to form a glass solidified body.

The iron component and the silica component of the glass solidified body are the iron component and the silica component mainly contained in the vitrification material. In addition, the basic component of the glass solidified body is the Ca component of calcium arsenate, the Ca component, the Na component contained in the vitrification material, and the like. The amount of basic components is the total amount of these basic component oxides, and in the glass solidified body containing sodium and calcium as basic components, the amount of basic components is the total amount of Na ₂ O and CaO.

If the weight ratio (Fe/SiO ₂ ) of iron to silica in the glass solidified body is less than 0.5 or exceeds 0.9, in the elution test of the glass solidified body (elution test according to Ministry of the Environment Notice No. 13), the amount of arsenic The amount of elution exceeded the environmental benchmark (0.3 ppm). Also, if the amount of basic components of the glass solidified body, for example, the total amount of Na ₂ O and CaO is less than 14 wt %, the arsenic concentration is less than 5 wt %, and the economic advantage decreases, and if the total amount of Na ₂ O and CaO exceeds 26 wt % , the arsenic concentration becomes 15% by weight or more, and the elution amount of arsenic increases, which is not preferable.

The upper limit of the heating temperature in the vitrification step is preferably 1400°C. When the heating temperature is 1450° C. or higher, calcium arsenate is decomposed and arsenic oxide is volatilized, and arsenic cannot be fixed. On the other hand, the lower limit of the heating temperature is the temperature at which the mixture of calcium arsenate and vitrified material melts. Usually, the temperature of the vitrification step may be 1000°C to 1400°C, and preferably 1100°C to 1350°C. The heating and melting time may be approximately 15 minutes to 30 minutes. The heating method is not limited as long as it is a method that can achieve the above-mentioned heating temperature. Usually, a melting furnace or the like can be used.

Regarding the arsenic-containing glass solidified body produced by the arsenic fixing method of the present invention, the arsenic concentration contained in the glass solidified body should just be 5 wt % or more and 15 wt % or less. When the arsenic concentration of the glass solidified body is less than 5% by weight, there are few economic advantages. On the other hand, in order to increase the arsenic concentration of the glass solidified body to exceed 15 wt %, calcium arsenate having a CaO concentration of 26 wt % or more needs to be used, and since the CaO concentration of the glass solidified body also becomes high and exceeds the level according to the present invention The amount of alkaline components in the treatment method increases, so the elution amount of arsenic increases.

Hereinafter, examples and comparative examples of the processing method and the arsenic-containing glass solidified body according to the present invention will be shown together.

[Example 1]

100 g (dry mass) of copper arsenide-containing mud (As: 30 wt %, Cu: 60 wt %) was mixed with 0.5 L of caustic soda solution (NaOH concentration 65 g/L), stirred and heated to 85°C while blowing air 1 L/min, while carrying out oxidative leaching. The leaching solution was subjected to solid-liquid separation and the sodium arsenate solution was recovered. 32 g of slaked lime was added to 500 ml of this sodium arsenate solution (As: 39 g/L, pH 10, 50° C.), followed by stirring for 4 hours to form a white precipitate (calcium arsenate precipitate). The precipitated slurry was subjected to solid-liquid separation, and 64 g (dry mass) of calcium arsenate precipitate (As: 30 wt %, Ca: 35 wt %) and 500 ml of filtrate (As: 20 ppm, NaOH 41 g/l) were recovered.

A vitrified mixture of copper slag and silica sand was added to the recovered calcium arsenate so that the weight ratio of iron to silica and the amount of basic components (total amount of Na ₂ O and CaO) became the values in Table 1. materials to prepare mixed samples. This mixed sample was put into a crucible, heated at 1350° C. and atmospheric pressure for 30 minutes, and melted. The melt is cooled and the glass solidified body is recovered. The elution test of arsenic was performed on this glass solidified body (in accordance with Ministry of the Environment Notice No. 13). The composition of the glass solidified body and the results of the arsenic elution test are shown in Table 1 (Sample No. 1 to No. 6).

As shown in Table 1, the samples No. 1 to No. 6 of this example are all limited as follows: the weight ratio of iron to silica is in the range of 0.5 to 0.9, and the amount of basic components is in the range of 14% by weight to 14% by weight. Within the range of 26% by weight, the elution amount of arsenic was 0.28 ppm or less.

[Table 1]

[Example 2]

A mixture of copper slag and waste glass was used as a vitrification material, and in the calcium arsenate recovered in Example 1, the weight ratio of iron to silica and the amount of alkaline components (total amount of Na ₂ O and CaO) were used. ) was added so that the value in Table 1 could be obtained to prepare a mixed sample. This mixed sample was put into a crucible, heated at 1350° C. under atmospheric pressure for 30 minutes, and melted. The melt is cooled and the glass solidified body is recovered. The arsenic elution test was performed about this glass solidified body (in accordance with Ministry of the Environment Notice No. 13). The composition of the glass solidified body and the results of the arsenic elution test are shown in Table 2 (Sample No. 21).

As shown in Table 2, the sample No. 21 of this example is limited as follows: the weight ratio of iron to silica is in the range of 0.5 to 0.9, and the amount of the basic component is in the range of 14 to 26 wt % Inside, the elution amount of arsenic was 0.3 ppm or less.

[Table 2]

[Comparative Example 1]

Copper slag to which silica sand was not added was used as a vitrification material, and in the calcium arsenate recovered in Example 1, the weight ratio of iron to silica and the amount of alkaline components (total amount of Na ₂ O and CaO) were used. The copper slag was added so that it might become the value of Table 3, and the mixed sample was prepared. This mixed sample was heated and melted in the same manner as in Example 1 to produce a glass solidified body. About this glass solidified body, the same arsenic elution test as Example 1 was performed. Table 3 shows the composition of the glass solidified body and the results of the arsenic elution test.

As shown in Table 3, since there are many iron components in the copper slag used as a vitrifying material, even if the weight ratio of iron and silica is 0.9 or more, the amount of basic components is in the range of 14% by weight to 26% by weight. The elution amount of arsenic also exceeded 0.3 ppm (sample No. 31 to No. 32).

[Comparative Example 2]

As the vitrification material, waste glass to which copper slag was not added was used, and in the calcium arsenate recovered in Example 1, the weight ratio of iron to silica and the amount of alkaline components (total amount of Na ₂ O and CaO) were used. ) was added to the value in Table 3 to prepare a mixed sample. This mixed sample was heated and melted in the same manner as in Example 1 to produce a glass solidified body. About this glass solidified body, the same arsenic elution test as Example 1 was performed. The composition of the glass solidified body and the results of the arsenic elution test are shown in Table 3 (Sample No. 33).

As shown in Table 3, since there are many basic components in the waste glass of the vitrification material, the amount of basic components exceeds 26% by weight, and the elution amount of arsenic exceeds 0.3 ppm.

[Comparative Example 3]

Copper slag and waste glass were used as vitrification materials, and in the calcium arsenate recovered in Example 1, the weight ratio of iron to silica and the amount of alkaline components (total amount of Na ₂ O and CaO) were The waste glass was added in the manner of the values in Table 3, thereby preparing a mixed sample. This mixed sample was heated and melted in the same manner as in Example 1 to produce a glass solidified body. About this glass solidified body, the same arsenic elution test as Example 1 was performed. The composition of the glass solidified body and the results of the arsenic elution test are shown in Table 3 (Sample No. 34).

As shown in Table 3, even if the amount of basic components exceeds 26% by weight, the weight ratio of iron to silica is in the range of 0.5 to 0.9, and the elution amount of arsenic exceeds 0.3 ppm (Sample No. 34).

[table 3]

Industrial Availability

In the electrorefining of copper, arsenic accumulated in the electrolyte solution can be fixed easily and at low cost by using inexpensive vitrification materials such as copper slag and silica sand. As a result, arsenic can be stably concentrated and stored for a long period of time.

Claims (2)

1. A method for immobilizing arsenic, characterized in that,

adding a sodium hydroxide solution and an oxidizing agent to copper arsenide-containing sludge as a copper arsenic-containing material, heating the mixture to perform oxidation leaching to leach arsenic,

solid-liquid separation of the leaching residue, addition of slaked lime having a Ca/As molar ratio of 1.7 to 2.0 to the recovered sodium arsenate solution to produce calcium arsenate,

in the recovered calcium arsenate, the weight ratio of iron to silicon dioxide in the glass solidified body is 0.5-0.9, and Na is used₂The calcium arsenate is formed into the glass solidified body by adding a vitrification material containing iron, silica and an alkali component so that the amount of the alkali component of the total amount of O and CaO is 14 to 26 wt% and the arsenic content is 11 to 15 wt%.

2. The method for immobilizing arsenic according to claim 1, wherein,

hydrated lime is added to a sodium arsenate solution to produce calcium arsenate, the solution containing the calcium arsenate is subjected to solid-liquid separation to recover the calcium arsenate, and a filtrate containing sodium hydroxide is returned to the oxidation leaching step and reused as an alkali source for the oxidation leaching.

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